In a slender essay titled “Here Is New York,” E.B. White wrote about the implausibility of the great city, mentioning among other things the millions of gallons of water needed each day just so people could brush their teeth.

If you read it — and you should — you will be very thirsty. And you will never flush again with the same nonchalance.

Somewhere between implausible and insane lies this little fact: The main way Americans use water at home is flushing the toilet. That is, 18.5 gallons per day per person. And the water is as pure as the drinking water that runs from our taps. Translation: 5.7 billion gallons of clean drinking water down the toilet each day.

Such numerical musings are plentiful in Fishman’s deliciously fun book. He has a way with numbers, making the inconceivable accessible. Example: The total water on the surface of the Earth makes up 0.025 percent of the mass of the planet. Or, “If Earth were the size of a Honda Odyssey minivan, the amount of water on the planet would be in a single, half-liter bottle of Poland Spring in one of the van’s 13 cup holders.”

You don’t say.

Busting water myths is one of many tools in Fishman’s tackle box. His larger purpose is to create an understanding of humanity’s relationship to water in hopes of diverting a water crisis that is, in fact, upon us. But “crisis” it need not be. From Fishman’s perch as he studies waterfalls created both by God and by man (not to mention families of sharks in the Las Vegas desert), water is plentiful but unappreciated and mismanaged.

Another factoid to whet your thirst: Water cannot be destroyed. In fact, every molecule of water on the planet has been here since the beginning, or about 4.4 billion years. The water you drink from a Dasani bottle very likely passed through the kidney of a dinosaur.

Here’s the really great news: You can always clean water up to make it drinkable; you can’t use it up. Almost all water problems are local and solvable and are really people problems, not water problems. And unlike other crises — economic, climate, health — solutions are at hand and affordable. Americans spend $21 billion a year on bottled water, while $29 billion is spent on maintaining and improving water infrastructure. Add to your calculation the following: The U.S. loses 7 billion gallons of drinking water a day through leaking mains.

Fishman’s immersion in water world was so exhaustive he even toted pails of water on his head with village girls in Jargali, India, just to see what it was like. Investigative journalism is rarely as entertaining as it is informative, but Fishman manages both feats. At times rhapsodic in his descriptions of the world’s truest natural wonder, he is ultimately optimistic despite his pronouncement that the Golden Age of water, free and abundant, is over.

Many nations and even some U.S. cities and towns already suffer water shortages. Forty percent of the world either doesn’t have good access or has to walk to get water. Each year, 1.8 million children die from lack of water or from tainted water. By 2050, the world’s population will have increased by 2.4 billion people. And, as Fishman notes, “They will be thirsty.”

Fishman described his optimism in an interview: “From the poorest neighborhoods of Delhi, where people make $1 a day, to the most advanced IBM factories, people are solving their water problems. They are grabbing hold and saying, we can figure this out. And they are.”

Already cities such as Las Vegas have found ways to conserve water through innovation and cooperation. Golf courses have removed large swaths of grass; mega-laundromats that wash thousands of hotel sheets daily have created technologies to clean and reuse water.

All fun aside, the purpose of Fishman’s journeys — to Australia and India, to an IBM factory in Vermont and the largest soup factory in the world in Ohio — was to see water clearly and get us to see it clearly. To that end, “The Big Thirst” is more than a drop in the bucket.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.